[clang] Remove intrusive reference count from `DiagnosticOptions` (#139584)

The `DiagnosticOptions` class is currently intrusively
reference-counted, which makes reasoning about its lifetime very
difficult in some cases. For example, `CompilerInvocation` owns the
`DiagnosticOptions` instance (wrapped in `llvm::IntrusiveRefCntPtr`) and
only exposes an accessor returning `DiagnosticOptions &`. One would
think this gives `CompilerInvocation` exclusive ownership of the object,
but that's not the case:

```c++
void shareOwnership(CompilerInvocation &CI) {
  llvm::IntrusiveRefCntPtr<DiagnosticOptions> CoOwner = &CI.getDiagnosticOptions();
  // ...
}
```

This is a perfectly valid pattern that is being actually used in the
codebase.

I would like to ensure the ownership of `DiagnosticOptions` by
`CompilerInvocation` is guaranteed to be exclusive. This can be
leveraged for a copy-on-write optimization later on. This PR changes
usages of `DiagnosticOptions` across `clang`, `clang-tools-extra` and
`lldb` to not be intrusively reference-counted.

1 files changed, 5 insertions, 5 deletions

diff --git a/clang/tools/libclang/CIndexCodeCompletion.cpp b/clang/tools/libclang/CIndexCodeCompletion.cpp
index 850c004..8f6729b 100644
--- a/clang/tools/libclang/CIndexCodeCompletion.cpp
+++ b/clang/tools/libclang/CIndexCodeCompletion.cpp
@@ -256,8 +256,8 @@ struct AllocatedCXCodeCompleteResults : public CXCodeCompleteResults {
   /// Allocated API-exposed wrappters for Diagnostics.
   SmallVector<std::unique_ptr<CXStoredDiagnostic>, 8> DiagnosticsWrappers;
 
-  IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts;
-  
+  DiagnosticOptions DiagOpts;
+
   /// Diag object
   IntrusiveRefCntPtr<DiagnosticsEngine> Diag;
   
@@ -356,9 +356,9 @@ static std::atomic<unsigned> CodeCompletionResultObjects;
 
 AllocatedCXCodeCompleteResults::AllocatedCXCodeCompleteResults(
     IntrusiveRefCntPtr<FileManager> FileMgr)
-    : CXCodeCompleteResults(), DiagOpts(new DiagnosticOptions),
+    : CXCodeCompleteResults(),
       Diag(new DiagnosticsEngine(
-          IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs), &*DiagOpts)),
+          IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs), DiagOpts)),
       FileMgr(std::move(FileMgr)),
       SourceMgr(new SourceManager(*Diag, *this->FileMgr)),
       CodeCompletionAllocator(
@@ -369,7 +369,7 @@ AllocatedCXCodeCompleteResults::AllocatedCXCodeCompleteResults(
     fprintf(stderr, "+++ %u completion results\n",
             ++CodeCompletionResultObjects);
 }
-  
+
 AllocatedCXCodeCompleteResults::~AllocatedCXCodeCompleteResults() {
   delete [] Results;